1. Field of the Invention
The present invention relates to a fiber type wavelength conversion element, and in particular to a fiber type wavelength conversion element using Cherenkov radiation type phase matching.
2. Description of Background Information
A wavelength conversion element is already known, in which an optical waveguide is provided using non-linear medium, a light wave is guided into extremely small regions, and the second higher harmonics of light are efficiently generated. This wavelength conversion element is roughly divided into the following two types according to the method to satisfy the phase matching: One is a type in which the phase velocity of a non-linear polarization wave excited from incident light is equalized with that of the second higher harmonics and phase matching is performed between the fundamental wave, i.e. waveguide mode of incident light, and a waveguide mode of the second higher harmonics. The other is a type in which so-called Cherenkov radiation type phase matching is performed between a waveguide mode of a fundamental wave and a radiation mode of the second higher harmonics.